Distribution Characteristic And Source Apportionment Of N-alkanes In The Atmospheric Aerosols Of Nanchang

The natural background value of n-alkanes is very small in the natural environment, but the concentration of alkanes increased gradually with the enhancement of human activities, which becomes more and more seriously harm to human’s health. In this research, sampling points are distributed in Nanchang urban area(the sixth floor roof of Analysis and Testing Center in the old campus of Nanchang University) and in Nanchang suburb (the sixth floor roof of Environmental building in Qian Hu campus of Nanchang University). PM2.5and PM10were collected from august5th to September6th,2012, and from November12th to December23th,2012. Analysis of n-alkanes pollution status by Ultrasonic wave extraction and GC-MS. This study reports the mass concentration of PM2.5and PM10, the concentration levels or distribution characteristics and sources of n-alkanes. The results show that:(1) The daily mean density’s average of PM2.5and PM10in the suburb is54.20μg/m3and107.98μg/m3, respectively. The range of them is49.16～65.15μg/m3and101.24～130.31μg/m3, respectively.In the urban area, the daily mean density’s average of PM2.5and PM10is96.40μg/m3and160.32μg/m3, respectively. The daily average concentration range is80.32～107.16μg/m3and153.16～168.76μg/m3.(2) In Nanchang suburb, as PM2.5, the mass concentration range of n-alkanes in atmospheric aerosol is respectively14.95～64.63ngm-3in summer and8.01～112.9ngm-3in winter.as PM10, it is23.96～106.37ngm-3in summer and8.94～120.35ngm-3in winter.In Nanchang urban area, as PM2.5, the mass concentration range of n-alkanes in atmospheric aerosol is respectively102.45～273.51ngm-3in summer and83.64～385.32ngm-3in winter.as PM10,it is163.92～327.61ngm-3in summer and92.01～436.86ngm-3in winter.(3) In the suburb, the main peak carbons in the n-alkanes of PM2.5and PM10are C27and C25in summer and winter.And they are C22and C24in the urban area. According to the peak distribution of n-alkanes from two seasons, the low carbon number alkyl hydrocanbons have higher concentration than the high carbon number alkyl hydrocanbons in winter, while it is contrart in summer. The concentration of n-alkanes in winter higher than that in summer. In winter, n-alkanes is easier to be enriched in the fine particulate matters.And in summer, n-alkanes is easier to be enriched in the coarse particulate matters.(4) The CPI of PM2.5and PM10samples is1.83-2.70during summer and winter of Nan Chang suburb and the average is2.16. In the urban, the CPI of PM2.5and PM10samples is1.11～1.75during summer and winter, the average is2.16. It shows that the n-alkanes in atmospheric aerosol of Nanchang are both of biogenic and anthropogenic characteristics. When the CPI1is0.57～0.72, it reflects that the contribution of human activities such as automobile exhaust to n-alkanes (<C2s) higher than biological source. When the CPI2is1.09～1.27, reflecting the emission from wax in higher plants is the main source of high carbon number n-alkanes (>C26) in atmospheric aerosol of Nanchang.(5) The parameters%waxCn show that the contribution of biological source to the n-alkanes in atmospheric aerosol is50.08%～51.42%in Nanchang suburb, reflecting the n-alkanes in atmospheric aerosol of suburb are mainly from biological source. However, in Nanchang urban, the contribution of biological source to the n-alkanes in atmospheric aerosol is25.42%～31.34%,reflecting the urban atmospheric aerosol n-alkanes from anthropogenic sources.